Lawmakers in states with a high concentration of federal employees are reacting to rumors that negotiators are considering a 5.5 percentage point increase in how much federal employees would contribute toward retirement plans. Maryland is home to some 300,000 federal workers.

The reaction is preemptive at this point. While House Republicans — and President Obama — have previously proposed cuts for federal workers, it’s not yet clear whether the provision is included in the emerging budget deal intended to avoid another government shutdown next month.

“I must tell you, in all candor that I am outraged by reports that one option being considered in the Budget Conference Committee is to increase the payroll contribution federal workers make to their defined benefit pensions,” Cardin, a Maryland Democrat, wrote to Senate Majority Leader Harry Reid. “No other group of predominantly middle class Americans has contributed to deficit reduction the way federal workers have.”

Democratic members of Maryland’s congressional delegation have pushed hard on the issue in recent days. Negotiators have until Friday to strike a deal on a budget agreement otherwise attention will likely shift to a Jan. 15 deadline to simply avoid anonther government shutdown.

Cardin also released a preliminary Congressional Research Service report he requested outlining the $115 billion in cuts the federal workforce has been hit with so far, including a pay freeze that began in 2010 and higher retirement contributions for new federal employees that were required in 2012.